The present invention relates to a device for sealing a port or fitment on a thermoplastic film.
There are well known machines for manufacturing pouches or bags having a port or fitment constructed from a thermoplastic film. In one step of the manufacturing process of such bags, the ports or fitments must be sealed on the thermoplastic film, generally perpendicular to perforations which have previously been made in the film. The sealing of the port or fitment on the film may be done either by ultrasound, or by a sealing member that is continuously heated, or even by means of a heating resistance intermittently fed an electric current.
In an embodiment of the invention, the present invention relates to a sealing device that includes a welding head with a heating resistance intermittently fed an electric current, and more specifically a ring-shaped heating resistance designed to create a circular seal, for an electric current around a tubular member of the port or fitment to be fixed on the thermoplastic film. In that case, the ring-shaped heating resistance is fed an electric current by means located at two diametrically opposed points. In known devices, an overheating generally occurs at a level of connection between the current supply means and the heating resistance, so a high risk exists that thermoplastic material will be deposited on the heating resistance. This causes a gumming up of the heating resistance and the necessity of an intervention.